Ship response results from the first operational season aboard the container vessel S.S. Boston

I

S SC-212

TECHNICAL REPORT

on

Project SR-182, "Ship Instrumentation and Data Analysis"

tothe

Ship Structure COmmittee

SHTP RESPONSE RESULTS FROM

THE FIRST OPERATIONAL SEASON

_ABOARD.

THE CONTAINER VESSEL S.S. BOSTON

by

R. A. Fain, J. Q. Cragin and B. H. Schofield

Teledyne Materials Research

Waltham, Massachusetts

under

Department. of the Navy

Contract N00024-68-C-5486

This doownent has been approved for public release and

sale; its distribution is unlimited.

U.S. Coast Guard Headquarters Washington, D. C.

ABSTRACT

This report contains data, with associated discussions,

col-lected from the SEA-LAND Vessel

SS Boston,

during the winter operating

sêason

November 1968 to April 1969 in the North Atlantic.

Ship's

voyages 7, 9, and 10

were manned by Teledyne personnel with data

col-lecte duri.ng each Atlantic crossing.

A total of 356, 15-minute data

intervals was obtained,

and three wave buoy launches

were performed.

Plots of various transducer outputs versus Beaufort sea state are

pro-vided along with comparisons with data from a similar class of

vessel.

PAGE INTRODUCTION. H

EQUIPMENT AND PROCEDURES . .

. 1

RESULTS OF 1968- 1969 SEASON

.. . . .12

DISCUSSION OF RESULTS .23

CONCLUSIONS

32

REFERENCES ₃₃

APPENDIX A

- TRANSDUCER SPECIFICATIONS

34

APPENDIX B - CALIBRATION MODE CALCULATIONS

35

Capt. W. .R. Riblett, USN

Head, Ship Engineering Division Naval Ship Engineering Center

Capt. 1. .J.. Banvard, USN

Maintenance and Repair Officer Military Sea Transportation Service

NAVAL SHIP RESEARCH & DEVELOPMENT CENTER Mr. A B.. Stavovy - Alternate

MILITARY SEA TRANSPORTATION SERVICE

Mr. R. R. Askren - Member

Lt. 3. G. T. E. Koster, USN - Member

SHIP STRUCTURE COMMITTEE

The SHIP STRUCTURE COMMITTEE, is constituted to prosecute a research program to improve the hull structures of ships by an extension of knowledge pertaining to design, materials and methods of fabrication.

RADM W. F. Rea, III, USCG, Chairman Chief, Office of Merchant Marine Safety

U. S. Coast Guaid. Headquarters

Mr. E. S. Dillon ', Deputy Chief

Off iqe of Ship Construction,

Maritime Administr&tion

Mrc C. '. L. 'Schoefer, Vice President

American Bureau of Shipping

SHIP STRUCTURE SUBCOMMITTEE

The SHIP STRUCTURE SUBCOMMITTEE acts for the Ship Structure Comittee on technical matters by providing technical coordination for the determination of goals and objéctivës of the program, and by evaluating and interpreting the results in terms of ship structural design, cónstruçtion and operation.

NAVAL SHIP ENGINEERING CENTER

Mr. J. B: O'Brien - Acting Chairman

Mr. J. B. O'Brien - Contract Administrator Mr. G. Sorkin - Member Mr. H. S. Sayre - Alternate Mr. I. Fioriti Alternate MARITIME ADMINISTRATION Mr. F. Dashnaw - Member Mr. A. Maillar - Member Mr. R. Falls - Alternate. Mr. W. G. Frederick - Alternate

AMERICAN BUREAU OF SHIPPING Mr. S. G. Stiansen - Member Mr. F. J. Crum - Member

OFFICE OF NAVAL RESEARCH

Mr. J. M.. Crowley - Member

Dr. W. G. Rauch - Alternate

U. S. COAST GUARD

LCDR C. S. Loosmore, USCG - Secretary

CDR C. R. Thompson, USCG - Member

.LCDR J. W. Kline, USCG - Alternate

Capt. L. A. Colucciello, USCG - Alternate

NATIONAL ACADEMY OF SCIENCES

Mr. A. R. Lytle, Liaison Mr. R. W. Rumke, Liaison

Prof. R. A. Yagle, Liaison

SOCIETY OF NAVAL ARCHITECTS & MARINE ENGINEERS

Mr. T. Buermann, Liaison

AMERICAN IRON AND STEEL INSTITUTE

Mr. J. R. LeCron, Liaison

BRITISH NAVY STAFF

Dr. V. Flint, Liaison

CDR P. H. H. Ablett, RCNC, Liaison

WELDING RESEARCH COUNCIL

Mr. K. H. Koopman, Liaison Mr. C. Larson, Liaison iv

Fig. 1.

Container Vessel S. s. Boston

1.0 INTRODUCTION

The container vessel S. S. BOSTON, Figure 1, is owned and operated by Sea-Land Service Incorporated. This vessel was formerly the S. S. GENERAL M. N. PATRICK, a C4-S-A1 personnel carrier, and was subsequently converted to a C4-X2 container ship by Todd Shipyards Corporation, Galveston Division, in. early 1968.

Teledyne Materials Research, Waltham, Massachusetts, designed and installed a ship response instrumentation system starting in June of 1968 and began collect-ing data in December of 1968. A comprehensive discussion of the instrumenta-tion system can be found in reference 1. The vessel operated on a route between Port Newark, New Jersey, U.S.A., and ports in Europe. Duriiig the period from late November 1968 to April 1969, a Teledyne engineer was aboard the vessel to operate the instrumentation system and to perform on-board data analysis. Data was ob-tained utilizing a fifteen-minute sampling every four hours during normal condi-tions with the option to switch to continuous recording during periods of high sea states. A total of 356 data intervals was collected during the past operating

season.

In addition to ship response information, simultaneous sea state informa-tion was obtained by launching "wave buoy" units which provide sea state spectra upon data analysis. Three such launches were made during the past season. A summary of the voyages undertaken, along with the number of intervals of data obtained, is presented in Table I. Table II summarizes the characteristics of the S. S. BOSTON.

2.0 EQUIPMENT AND PROCEDURES

2.1 Data Acquisition Instrumentation Systems

Two functionally separate, but physically common, instrumentation sys-tems were installed aboard the S. S. BOSTON. The ship response system was operated

2

Table I. 1968-1969 Voyage Summary

Ship's VOyage #7

-Number Number

of

ofData

From On To On Channels. Intervals

Newark 12/19/68 Rotterdam 12/30/69 7 48

Rotterdarn 1/9/68 Rotterdam 1/14/69 11 24

Rotterdam 1/14/69 New York 1/24/69 14 49

Ship's. Voyage #8

Involved movement of the vessel from Todd Shipyard, Brookly., New

York upon conclusion of the longshoremen's str-ike.

Ship's Voyage #9

Number Number

of

ofDatâ

From /'. On To On ChànnOls

Intervals---Newark 2/21/69 Rotterdaxn 3/3/69 14 63

Felixstowe, 3/10/69 Newark . 3/18/69 14 58

England

Wave buoy launched at 1500 () On 2/25/69. Serial No. 49004

Ship's Voyage #10

-Number Number

of of Data

From On . To . . On Channels. Intervals

Baltimore 3/23/69 Rotterdam 4/1/69. 14 58

Felixstowe 4/10/69 Newark 4/19/69 14 56

Wave. buoy launch 1345 GMT 3/30/69 - Serial No. 49001

Table II.

Characteristics of

S.S. BOstOn

Original Name; GEN. M. N. PATRICK

Builder: Kaiser Richmond (Hull #16)

Converter: Todd Shipyards Corporation

Galveston Division (Hull #87)

Type: C4-5-Al converted to C4-X2

Cöñtainer Ship

Official. Number: 511585

Length Overall: 522' 10-1/2"

Length Between Perpendiculars: 496' -0"

Breadth, Molded: 71' - 6"

Depth, Molded to Upper Deck Side: 45' - 6"

Depth, Molded to Second Deck: 35' - 0"

Double Bottom Depth 5' - 0"

Tonage (U.S.) Gross: 11,521.77

Net: 7,607.00

Load Draft, Scantling 30' - 6

Full Load Displacement: 20,250 Tons S. Water

Light Ship Draft 17' - 8"

Dead weight: 9,317

Center of Gravity (Full Load): l.c.g. 1.35' aft of midships HP.

v.c.g. 27.04' above base line

Light Ship: l.c.g. 1.13' fwd of midships BP

v.c.g. 18.2' above baèe line

Block Coefficient _{0.654 (30' Molded Design Draft)}

0.61 (18' Typical Present Operation)

Prismatic. Coefficient _{0.664 (30' Molded Design Draft)}

0.628 (18' _Typical Present Operation) Waterplane Coefficient

0.752 (30' Molded Design Draft) 0.685 (18' Typical Present Ope±ation) Midship Section Modulus

39,391 in2 Pt. to Top of Upperdeck. Machinery:

Steam-Geared Turbine

Shaft Horsepower - Max. Coat. _{9,900 S.B.P.}

Propeller (1)

5 Biaded 21' - _8" Dia.

Container Capacity (No) ₃₆₀

Container Geometry:

_L-35'-O"

W - 8' 0" Ii - 8" - 6-1/2"

primarily in an automatic mode with a 15-minute sampling of data every four (4)

hours. The system can be run continuously by switching to manual. The second system is n accelerometer wave buoy system with a free-floating wave buoy as the signal source. Data was recorded siuniltaneously on both systems during the buoy launch for a period of approximately 90 minutes depending upon the received signal strength.

2.1.1 Ship Response Instrumentation System

The ship response instrumentation presently installed aboard: the S. S. BOSTON is designed to provide 14 channels of data for recording on an Ampex FR-1300 FM tape unit (Figure 2). Two categories of signals are monitored:

channels 1 - 4 record signals developed from strain gage bridge circuits

(Figure 3A to 3D) while channels 5 - 13 monitor the outputs of transducers located throughout the ship to sense accelerations and displacements. channel 14 is a compensation channel used in the playback mode to correct recorder error

contribu-tions. Detail transducer specifications can be found in Appendix A, while

Figure 4 presents a schematic view of the various transducer locations. A complete listing of channel assignment is provided in Table III. A discussion of the trans-ducer calibration mode calculations is provided in Appendix B.

A

0

_.-0

/

Fig. 2. 14-Channel Shipboard Tape Recorder AMPEX FR1300

Note: Gages at bath locations dre t,.-ans strain gagis. each ens 120 ohms set at 45 at the local vertical.

Baa

Fig. 3C. Bridge Circuit-Torsional. Shear Stress (Channel 3)

Note: All Bridge Elanents are 448 iiStièss Gages.

Note: Elanents at gage looatlóg are 448 ohm stress gages. Bride

completion resisters are a mat9ed pair of 500 olmo resistors.4

Fig. 3D. Single Element Strain Gage Bridge Circuit (Channel 4)(4A-SUDG-Starboard Underdeck Gage, 4B-SSPG-Star-board Side Plate Gage, 4C-SBBG- Box Beam Gage, 4D-PSWGPort side Weld Gage.)

Fig. 3A. Bridge Circuit-Vertical Fig. 3B. Bridge Circuit-Horizontal

Longitudinal Bending (Channel 1) Longitudinal Bending (Channel 2)

S tbd

View AA

Port

Transducers at Midship Section Including Box Beam Gages

® Bi-dirëctional accelerometer (horizontal-vertical)

0

Pendulum transducers for pitôh and ±011 Stress gage transducer

30-inch gage length displacement transducer

\J

Torsional -sttain gage: bridge

Single element stress gages, longitudinal orientation

Fig. 4. Schernati View of Various Transducer Locations on

S. S. Boston

LA

The selected stress indicated for channel 4 of Table III relates to the stress gages applied to variOus areas of the box beam to obtain a measure of stress distribution in. this structure. Figure '5 shows the location of these

four gages.. These elements were monitored ona time-sharing basis during a

Voyage. .

Figure 6 is. a view of the iflsttument console installed aboard the S. S. BOSTON. . previously stated, reference 1 should be consulted for details

of the system.

n effort was made to acquire, wherepossible, data of the same type as that collected from the S. S. WOLVERINE STATE during a period of several years. Accelerometers were located at approximately the same position on the S. S. BOSTON

i e , forward, midship, and aft, so that data could be compared for similar

cros-sings. The midships. vertical bending moment is also of primary interest,, and data from both ships- is considered in this report.

2.1.1.1 SupplementaryStraiu Gages

In- order to assess the possible presence of local effects due to the extremely short -gagelength of the stress gage transducers (approximately 1/4 inch)' an alternate form of strain gage was also incorporated into the instru-mentation system This supplementary gage was previously referred to as a

dis-placement gage -in reference 1. This latter device consists of an electrical Channel

Table III Tape Recorder Channel Assignment

Function Source

1 Vertical Longitudinal Bending Strain Gage Bridge

2 Horizontal Longitudinal Bending Strain Gage Bridge

3 Torsional Stress Strain Gage Bridge

4 Selected Stress Strain Gage Bridge

5 Stern Vertical Acceleration Accelerometer

6 Stern Hor4zontal Accélétation Accelerometer

7 Midships Vertical Acceleration Accelerometer

8 Midships Horizontal Acceleration Accelerometer

9 Pitch Pendulum

10 Roll Pendulum

11 Bow Vertical Acceleration Accelerometer

12 Bow Horizontal Acceleration Accelerometer

13 Longitudinal Pisplacement Supplementary Strain Gage

SUDC SBBG (86-87%) (99-100% 1-3/8" 14-1/2"

Chaünel No. 1 - Vertical bending

(100%) stress. transducer PORT 6 STBD 1 SSPG (94-95%) 53II PSWC) (eztren1y variable)' (Port Side) 1'

(

Approx. 22 Neutral Axis

j

NOTE: Percentages indicate value of vertical longitudinal bending

stress at location relative to 'Channel No. 1 value taken as

100 per cent.

Fig. 5. Location & Stresses of Box Beam Gages

Fig. .6. Teledyne Instrumentation

element (direct current differential transrortner) which provides an output signal proportional to displacement.. These transducers were arranged, by mechanical fixturing, to provide Output data. of the displacement over a 26-inch gage length,-significantly longer than that of the stress gage. The elements will accommodate displacements of ± 0.050 inches which represents capability of: measuring stresses of the order of ± 5.7,800 psi over the 26-inch gage length.

One each of these supplementary transducers was located,, port and starboard, underdeck just forward of the midship stress gage installations and oriented to provide longitudinal bending stress data. 'Since each transducer was monitored independently, the stress data from each contained both vertical and horizontal bending stresses.- Comparison of the total s.tress could be made against the algebraic sum of the data from the horizontal-and vertical bending stress transducers.. Outputs of the supplementary transducers were time shared on channel 13 of the tape recorder.

2.1.2 Accelerometer Wave Buoy System

The accelerometer wave buoy system consists of model 266 wave buoys together with the model 440 data acquisition unit for receiving and recording the output of the wave buoy. The principle of operation was that of measuring the rise and fall time of a moving body which is given an upwards impulse of fixed momentum relative to the case of the floating buoy This motion through mechanical linkage changes the induced voltage in a coil within the accelerometer

structure. The output is a train of pulses set to a zero accelerat-ion rate of 30 pulses per second. These pulses are used to key the radio transitittér for

relaying the buoy output to the shipboard receiver. .

-- The- operating frequency is in the range of 30 to 36 MHz and the

output power of the transmitter is approximately 5 watts.

-The model 440 wave data acquisition system receives and. processes - the transmitted wave buoy signal and records it on magnetic tape along with a

reference signal and voice annotations. le reference signal provides a fre-quenéy base for subsequent aothpensation of flutterand wow in the tape recording. The reference signal is a stable 150 Hz oscillator feeding one of the recorder channels while the buoy signal is recorded on the second channel The two

re-cording channels ae arranged in a standard four-track stereo configuration ef-fectively doubling the recording time when the reels are reversed The tape corder is run at a speed of 3-3/4- inches per second providing 60 minutes of re-cording t-ime on each pass of tape. The tape is computer processed with a power spectra of displacement and acceleration provided as an output signal. Details of this particular wave height measuring system can be found in reference

_2.

2.1.3 System Reliability, Maintainability and Operation

Based on the relatively short 1968-1969 operating season, the Teledyne Instrument System (consisting of the ship response system and wave buoy system) has proved extremely reliable. Reliability is generally defined -as the mathemati-cal probability that a device (equipment-system) will function within specified characteristics in a defined environment for a specified period of time

The system is usua.ly evaluated on its susceptibility to. failure, and the life of the systeth is expressed as the percent failure per thousand or million hourd of operation. A calculation of this type is impractical with the small amount of data available We will, therefore, consider the reliability of this system on thebasis of three major design areas i.e., electrical, mechani-cal, and environmental.

10

Electrically, once the final installation and adjustments were corn-plete, the system did not suffer downtime from electrical component failure. Initial design criteria was such that even a component failure would not cause a catastrophic reaction in the system. At worse, a reductiOn from a full 14-chan-nel capability to some lesser number of chan14-chan-nels would occur, and a priority assignment .of information desired has been established to assist the operator in making the most of the equipment available for on-line operation. The system was 100% efficient with no data intervals lost because of equipment malfunctions.

Two failures were encountered during the 1968-1969 season. The

first consisted of a shift to a fixed output level in one of the stern accelerom-eters on the homeward leg of voyage 10. The defective unit was replaced, and only a small amount of data for that channel was affected.

The second failure was the lack of transmission from the third wave buoy launched again on the return run of voyage 10. This apparently was a prob-lem inherent in the buoy itself as the system itself is still operating normally. A check of each buoy was made before each launch, and this unit functioned proper-ly until shortproper-ly after being set free.

Mechanically, other .than the replacement of a noisy bearing in the recorder unit at the completion of the season, there were no problems. The techniques used to mount all structures proved satisfactory even during extreme roll conditions. The equipment room environment, quite similar to normal labora-tory conditions, proved friendly to the equipment, and no problems due to tempera-ture, moistempera-ture, vibration or other environmental dynamics were encountered.

The system, based on operator reports, was functional in layout and provided accessibility to all major components. Maintenance, other than daily operational checks and routine operation, was not required to any extent during the past season. Only minor changes to the basic system or techniques are anti-cipated for the forthcoming 1969-1970 operating season.

2.1.4 Calibration of Vesâel Instrumentation

An attempt was made in August of 1968 to obtain a "calibration" of the instrumentation aboard the S. S. BOSTON while the double-bottom spaces were being filled with ballast mud over a 21-day period at Galveston, Texas. A

"calibration" by definiti6n is a sequence of tests involving bending the ship with known loads and reading strain data with the instrumentation system. This

cali-bration permits a comparison with computer calculations of the structure's be-havior and provides a verification of the integrity of the instrumentatiOn system.

Unfortunately, this test was not conclusive primarily due to the long period of the test, the extremes of temperature experienced and changes in the physical structure which were going on during the calibration sequence.

A comprehensive discussion of this test sequence and results achieved can be found in section 9.0 of reference 1.

A second calibration of the vessel was performed at Port Newark, N.J. on November 11 and 12, 1969, using preweighed containers to provide torsion and longitudinal bending moments. The complete report of this static test is in preparation and will soon be released. However, interpretation of the material to follow in this report may be aided by the observation that there was good agreement between calculated and measured torsion and bending stresses. A maxi-mum torsional shear stress change of about 850 psi was achieved during the test, and a maximum longitudinal vertical bending s.tress change of 2500 psi was observed just before the vessel sailed.

2.2 _{DATA.ACQUISITION PROCEDURES}

-2.2.1 _{Ship Response Instrumentation System}

When the vessel leaves port for an Atlantic ërossing, the operator normally has the system running in automatic _{mode This mode turns the system on}

for a period of 15 minutes every four hours Every 7-1/2 minutes, a zero-cali-bration sequence is repeated. (Note: _{This is a change from the original 5-minute}

sequence mentioned i-n section 6.0 of reference 1.) _{It was established, after the} first season of operating, that three _{zero-calibration-sequences obtained with the} 5-minute sequence were not- required but that _{one- ever}

7-1/2 minutes would be suf-ficient. _{Zero consists of opening the transducer s{nal}

lines and

rmnv1 of

excitation from bridge circuits for approximately 20 seconds. Observation of channel outputs during this interval establishes any shift in signal level due to amplifier or Other component drift.

The calibration period consists of shunting one arm of the bridge cir-cuits with a specified resistance (See Appendix B.) or, in the case of the other transducers, of substituting a calibration voltage. This sequence lasts approxi-mately 1 minute with the remainder of the period used to monitor all 14 channels

for data. The Teledyne operator keeps a running log book wherein he makes entries describing the sea and wind condition and descriptive ship parameters during the 15-minute recording interval. _{In addition, arrangements were made to have the} mate on watch keep an identical, but independent, log book so that a comparison of entries could be made. 1n general-, over the past season, agreement of the books was quite good.

-In addition to -this normal operating mode, the operator has set a "high stress level" so that in the event of stresses above the set limit, the system will turn on and record for a specified period. A high stress condition al-so sets off an alarm to alert the operator. The system can. be switched to a manu-al continuous recording mode at this time, in order to acquire a larger sampling of high stress data information.

During periods of low sea states, as in port, the operator continual-ly examined his data-by displaying various chamiels on an oscillograph play-back

unit. This procedure permits close examination of each channel to ensure t-hat the system is functioning

properly.-2.-22 Wave Buoy Instrumentation System

A wave buoy launch is generally performed when the sea and wind condi-tions meet preset condicondi-tions. A Beaufort sea state of 6 with either head or fol-lowing seas is considered to be a minimum requiement. The buoy to be launched is placed on deck, and after-installation of its-antenna, the power is turned on. In the equipment room the operator performs a checkout procedure and records on

tape the conditions associated with the launch. The ship response instrumentation-system is placed in a manual continuous record mode, and the wave data recorder is

turned on. The buoy is then lowered over the side and allowed to drift away from

the vessel. The operator continually monitors the receiver signal and adjusts his gain to keep signal at-recordable levels fOr as long a period as possible.

At loss of signal, both systems are.secured and appropriate entries made in the log book describing the launch sequence. The ship response -system is

returned to automatic operation and the wave tape removed, marked and prepared

-3.0 RSL1LTS. OF 1968 1969. SEASON

3.1 Sea States Profiles I

Tables IV, V a'4 VI graphically represent the frequency of occurrence of theva±ious Beaufott sea stáes during vo'ages 7, 9, and 10. These charts reflect the environmental conditions or background that prevailed throughout the periods of data acquisition and against which the ship tesponse datawas assessed,

Table IV. Sea State Profile _{Voyage #7 Dec. 21' 1968 - Jan. 23,1969}

Table V Sea State Profile

Voyage #9 Feb. 22, l969-t4rch 18, 1969 3, 30 20 15 10 3 4. 3 6 !EA STATE :12 7 S8A070 006

Table VI. Sea State Profile

Voyage #10 March 23, 1969-April. 19, 1969

1 2 3 4 3 6 006 25 10 55 30 20 15 10

iHHLi

Establishment of the exact sea state withàut wind speedor direction measure-ments was extremely difficult, and it is planned to provide this information during the 1969-1970 season. The data displayed reflects an input from both the Teledyne operator's and mate's logs for each data interval. The lack of data from January 23 to February 22, 1969, caused by the vessel's being ou of service due to the longshoremen's strike, is unfortunate; this time of the year being one of

the most severe for North Atlantic crossings. - -.

-3.2 Stress Data

Figures 7 - 9 represent the combined data from voyages 9 and 10 of

stress channels .1 - 3. The data from voyage 7 was deleted due to the 1.aryingnum-ber of channels recorded and thefluctuationin reording levels' 'experienced while the system was being adjusfed for opt-imuni ópertion. Each dta point was obtained by replaying the tape onto an oscillograph to create chart recordings of all

e-corded data. The maximum peak-to-peak value (i.e., peakto-trough for those nautically oriented) for each data interval was tabulated and then plotted against the Beaufort sea state established frO'e log book information. Each point repre-sents the maximum signal received during a 15-minute sampling period. Note that the peak-to-trough.value 'is approxImately twice the usual value used in most engineering computations:

Still Water Value

x1 x2 x Peak-to-trough (or peak-to-pea1) values. The maximum peak-to-trough value of vertical longitudthal bending shown on Figure 7-is 13,000 psi at a ea state of 9. A predominance of data is found between 3,000 and 7,000 In comparison the maximum peak-to-trough value of horizontal longitudinal bending as presented in Figure 8 is 3,000 psi. Very lit-le spread in signal lit-level is experienced even at tbe higWe± sea.state's. The maxi-mum peak-to-trough value of torsional shear stress observed during th 1968-1969 season, as shown o Figure 9, is approximately 1,260 psi at a sea state of 9.

The average value- of this -signal- acros the range, of- sea states i.e., 0 to 10 is consistently under- 1,000 psi. The maximum'stress seen on the four box beam gages were as follows:

(SIJDG) 13,800 psi at a sea state of 9

(SSPG) 5,500 psi at a sea state of 5

(SBBG) 8,000 psi 'at a sea state of 9

(PSWG) 8,000 psi at a sea state of 4

p

14 12 10 4 2 0 S. S.

_X

Ii.?.

::

S...

S...

OS

..

S. S.

I

-- I--S I

1.

'14 S

..

3EAUFORT. SEA STATE

Fig. 8.

S.S. Boston

Horizonta1Longitudinal Bending--Ch. 2 Voyages #9 & #10

5 OS S5flISS .5 -S. -.15

:..

5 1 5- SO -'_S. OS_nnsoSS '155

_Sm..

_fltO5*

1515

_.

.

-'

.

14

.

S 12

I

S. 10 S

xi

S.

.

S S

.

8

_.

_I SOS I cj 0 1 2 5 6 8 10

BEAUFORT SEA STATE

Note: X Indicates average value. .

Fig. 7.

S.S. Boston

Vertical Longitudinal Bending-Ch. 1 Voyages #9 And #10

0 1 6 10 4

x.

S S S S

.2 S

L

S 00

.

S S..

.

S S.

.,

S 10 1.4 1.2 1.0 0 .8 , .6 .4 p S. S.. .

..

::.

.S

S

.

. S

..

_S.

....

..

.

. S S. _. S S.

...

..

S. SSI.

..

S

..

..

S S 3 4 5 6

BEAIJFORT SEA STATE

Fig. 9.

S. S. Boston

_{Torsional Shear Stress-Ch. 3 Voyages #9 Arid #10}

It is not possible to compare these signals to each other at precisely te same instance of time, since only one of the four is recorded at any one time. How-ever, the operator, by judiciously switching the instrumentation, can obtain data on all ôhañnels over a short period of time during which consistent and comparable sea conditions are sustained.

It is of interest to note that the total numbe'r of data intervals used in the presentation corresponds to the tabulation of sea states on Tables V and VI, but not in total to the number of intervals tabulated on Table I. The difference between the two totals reflects the fact that 'some intervals recorded on leaving or entering port displayed little or no information and were thus not included in the analysis.

3.3 Acceleration Data

Vertical and horizontal acceleration data was obtained at three loca-tions aboard the S. S. BOSTON. These locations were chosen to be compatible with the installations aboard th S. S. WOLVERINESTATE in order to permit comparison

of data.

The stern transducer units are located on the forward side of frame 195 under the upper deck amidships. Outputs from these two units are plotted in Figures 10 and 11.

The midship transducers are located on the aft side of frame 112 under the second deck amidships. An attempt was made to install these units as close as practical to the loaded center of gravity o,f the vessel. The output of these accelerations is plotted in Figures 12 and 13.

1.4 1 2 UI .8 0

:

.6 2 0 S S.

.

S.! S.. !S 16.

EEORT SEA STATE

Fig. 10.

S. S. BOston

Stern Vertical Acceleration-Ch. 5 Voyages #9 & #10

S

...

..

.

..

..

..

:..

:.

- ..-S. . _S S..

..

...

S.

.

S S S S.

Fig. 11.

S.S. Boston

Stern Horizontal. Acceleration-Ch. .6 Voyages #9 & #10

- , -S

--

:

..'

-S S S. .SS5

:

:

S

:.

SSS

.

..

.

. S S SI.

SS

S .

:::...

$

:..

---I

-;

:'

1:::.... ;.

-

--S--

..-- - - -\

,--. c 7 8 1C 0 1

2.

3 4

.5

6 7 8 9 10

BEAUTORT SEA STATE

S S.

.

S. 1.4 1.2 1.0 .8 .6 .4 0

.7 .7 5 .1 0 0

Fig. 13.

S.S. Boston

Horizontal Acceleration-(Sway)-Ch. 8 Voyages #9 & #10

-S

S....

SS. S

-S S S S IS

:''

---.

S...

S S55

..

SS

-::...

-

...

::..

S -S

.

55 - I

-I I S.

::..

S. IISSS SSIS

I

It.

...

ISIS S.

.1

-IS. SI 55. I. -

---

. _._ S S. - S S

::.

I.S - S.. IS

..

..

-:::..

.555

::

55 ---IS

-:::

..

5555 SI

....

.

-I

S

---..

---I.

I5

::.

I

-.

- - _I - S

SSSS-S5.

S e.. S. - I S5 ISIS i I I ISIS

I---

SI 1 2 3 .. 4- 5

6

7 8 10

BEABFORT SEA STAiK

Fig. 12,.

S.S. Boston

P1idship Vertical-Acceleration-(Heave)-Ch. 7 Voyages #9.& #10

I 2 4 5 6 7 8 9 10

The bow àcce-IOrOmeter units are lOcated on the aft s-ide of frame 13 under the upper deck amidships. These outputs are shown in Figures 14 and 15.

The maximum peak-to-trough accelerations observed during voyages 9 and 10 were as follows: Stern Vertical -Stern-Horizontal -Midship Vertical Midship Horizontal -Bow Vertical -Bow Horizontal

-It is eacily seen that the vertical aàcelérations of both the bOw and stern present the highest signal output; the bow vertical is the larger of the two.

3.4 Ship's Motion Data

The motion of the ship is described by the outputs of fOur

trans-ducers. The midship accelerometer outputs of Figures 12.and 13 provide (heave)

1.4 1.2 1.0 .4 .2 ,0.86g at a 0.56g at a 0.25g at a O.27g at a l.02g's at 0.64g's at 18 sea state of .9

sea state of 3 and 10 sea state of 5

sea state of 5 a sea state of 9 a sea state of 9

Fig 14.

S.S. Boston

Bow Vertical Acceleration-Ch. 11 Voyages #9 & #10

. S -:

Xi:?

.:...

1:

I:.:.

__:

xr

-I,

p

-X.

X.

-.. S.. I !!

r

-_____

_S..

-

.S

--S

.:

-- -. --0 2 3 4

5

7

.8

9 10 BEAUP0B SE STAlE

1.4 2 1.0 .8 .6 .4 .2

fr:

.

I S -S S.

:

.

IS SOS0 .

...

Sill

.55* 8e. SO 5OS.

.

.

-S

.--SI S

-S..-,.

OSS S 551S

::r

__I

S. -S.

-2 3 4 5 6 9 10

BEAUFORT SEA STATE

Fig 15.

S.S.. Boston

Bow HprizOnta1 Acceleration-Ch. 12 _{Voyages #9 & #10} vertical acceleration and (srã) hOriontal aeleration. Añadditional package of two pendulum transducers at the same location provide a pitch and roll signal. This Information is presented in Figures 16 and 17.

The maximum double amplitude value of pitch observed is 10.2° at a sea state of 9.; while the maximum roll signal double amplitude is a 34° signal also at sea state of 9.

3.5 Supplementary Strain Gage Data

Data from the supplementary gages was obtained as, a voltage level upon play back of the recorded tape. A signal of ± 1.5 VDC is equivalent to

± 0 050" displacement by design This value in turn is equivalent to a stress of approximately 57,800 psi. Dynanic peak-to-trough variations in strain were readily observed, and it was a spot check of these values compared with data from channel 1 at the same interval of time which confirmed the validity of the

measurements.. To obtain a scale factor to evaluate the dynamic swings, it was necessary to feed a known voltage signal from an adjacent channel through the chan-nel 13 play back route and then rerun the displacement signal and compare values. Values of stress consistent with the data of Figure 6 were obtained.

3.6 Wave Buoy Data

A total of three wave buoys was launched during the 1968-1969 operating

season. The first launchwas buoy 49004 at 1500 GMT on February 25, 1969. Table VII is. a tabulation of the log book data for the period of the launch and Figures 18 and 19 present the power spectral density analysis associated with the wave

-1.4 12 10 -.

:

u°

z

.

,.

:

r

:°

_i:

_r"

V I

I

:::.._....:'..

V V V I

U

.

..

r

II

ISSOV

i_ I

1.

I

I

S S. S S S. -

._

1

.

. IC 11.1 V . 5

-- Ir'-.

I

115

r

I

3 4 5 6 S

I.

C V.. S. 20

BEAUFORT SEA STATE

-C

4 5 6

BEAUFöRT SEA STATE

8

Fig. 17.,

S.S. Bos*on Ro11-Ch.. 10

Voyages

#9 & #10

9 10

V

10

Fig 16. S.s.

BoBton

Pitch-Ch. 9 Voyages #9 & #10

35. C C I-30 25 20 C

.6.

C I. C I S 01 C I5 C S S 15 S. S C CC

I

Table VII.

Wave buoy Launch No.

1

Log Book Dta

Buoy Sëfiàl No.

49004

Voyage No. 9

Index Number 18

Date & Time '

1500 GMT '2-25-69

Time Meter Reading

4fl.9

Latitüde

49..2

N

Longitude 0. 7 'W

Course - - - O78

Speed

8.5

Knots

Engine 50 RPM

Wind Speed

45 Knots

Relative Wind Direction NE

Bëaufort Sea State No.

8-9

.ReThtive Wave Direction NE

Average Wävé Height

20 Ft.

Average Wave Period 5 Sec.

Average WVe Length

125 Ft.

Aierage Swell Height 25 Ft.

Average Swell Length

350

't.

Relative Swell Direction NE

Barometer Reading

_29.58

Sea Temperature

58°F

Air Temperature

469F

225

V

22

0 .1 2 3 4 5 6 . 7

FREQUENCY RADIANS/SEC

Fig. 18,

S.S. Boston

Buoy Serial 4.9004 Launched 2/25/69 Power Spectral Density Analysis Accelerometer Wave Buoy

TEE STANDARD DEVIATION OP TEE DISPLACEMENT SIGNAL IS 7.83 FT EMS

FREQUENCY RADIANS/SEC

Fig. 19.

S.S. Boston

Buoy Serial 49004 Launched 2/25/69 PowerSpectral Density Analysis Accelerometer Wave Buoy.

47 5 45.0 42.5 40.0 37.5 350 32.5 30.0 27.5 25.0 22.5 20.0 P17,5 .13.0 1.2.5 1.0.0 7.5 2.5 0

The second lai.inch was buoy 4.9001 at 1345 GMT March 30, 1969. Table VIII contains the log book data and Figures 20 and 21 display the power spectral den-sity analysis.

The third launch of buoy 49002 Occurred at 1015 GMT on April 12, 1969. Table IX contains the log book information, but unfortunately the buoy did not operate for a lông enough period to permit computer analysis.

4.0

DISCUSSION OF RESULTS

4.1 Sea State Profiles

The three sea state profiles of Tables IV, V and VI display the various sea states encountered during the 1968-1969 season. Voyage 9 was by far the most prod4ctive in high sea state readings followed by voyage 7 and 10. I.t is easily

observed that the sea conditions are somewhere between the states 2 and 6 for the. ma3orlty of the time Similar profiles will be generated for the 1969-1970 season, and it is anticipated similar results will be athieved after averaging all the

voy-ages.

Table VII. Wave Buoy Launch No. 2 Log Book Data

Buoy Serial No. 49001 Voyage No. 10

Index Number 42

Data & Time 1345 T 3/30/69

T1ie Meter Reading . 261.4

Latitude 49.8 N Longitude 19.1 W 0 Course 079 Speed 17 Knete Engine 85 RPM

Wind Speed 15 Knots

Relative Wind Direction w

Beaufort Sea State No. 5

Relative Wave Direction W

Average Wave Height 5 Ft.

Average Wave Period 6 Sec. '

Average Wave Length 8 Ft. *

Average Swell Height . 5-6 Ft. *

Average Swell Length. 20 Ft. *

Re1itie Swell Direction W

Barometer Reading 30.18

Sea Temperature 60°]F

Air Temperature ... 60° F

Weather - Cloudy

- The wave heights ad lengths are reported directly from the mate's log.

These data are subject to question, i.e. a 5 ft. wave height coincident with en 8 ft. wave length.

20 19 18 17 16 15 14 13 12 10 6 5 4 3 2 1 0 0

Fig. 20.

S.S. Boston

Buoy Serial No. 49001 Launched 3/30/69 Power Spectral Density Analysis Accelerometer Wave Buoy

14 13 12

11.

10

9.

8

7.

6-

5-

4-

3-2 I I

'I

I

I'

0 1 24

TEE STANDARD DEVIATION OF THE DXSPLACEMEifl SICR&L IS 2.81 PT EMS 3 4 FREQUENCY RADIANS/SEC 5 2 6 6 7

Fig. 21.

S.S. Boston

Buoy Serial No. 49001 Launched 3/30/69 Power Spectral Density Analysis Accelerometer Wave Buoy

3 4 5

Table IX.

Wave Buoy Launched No. 3: Log Book Data

BuO Serial No. 49002 - - Voyage No. 10

IndexNumber 14

Date & Time 1015 GMT 4/12/69

Time Meter Reading 181.6

Latitude 49° 46' N Longitude - O7° 15' W -0 Course .250 Speed 12 Knots Engine 75-80 RPM

Wind Speed - 25 Knots

Relative Wind Dirêtio SW

Beaufort Sea State No. 5-6

RelativéWave Direction SW

Average Wave Height -- 6 Ft. *

Average Wave Period 10 Sec. *

Avrage Wave Length 30 Ft. *

Average Swell Height' - 20 Ft.

*

Average Swell Length 150 Ft *

Relative Swell Directiot - SW

Barometer Reading 30.41

Sea Temperature 57° F

Air Temperature 58 F

Weather .. Cloudy

* See fOotnote on Table VlII

4.2 Stress Data

Figure 7 reflects the informatiOn from channel 1, vertical longitudinal bending, and is of prithary importance. This function-was monitored as-t1Bending

Moment" on. several previously, instrumented vessels.. The "X" at each sea state.

level, is. the average value for -that sea state, combining the voyage 9.and lO,'data-.

The highest peak-to-trough stress recorded aboard the S. S. BOSTON was approximate-ly 13,000 psi at a sea state of 9. The highest average value is a little over 10,000 psi occurring at sea states 9 and 10.

26

Figure 22 provides a comparison of the vertical bending stress data

from the S. S. BOSTON and S. S. WOLVERINE STATE. The S. S. WOLVERINE STATE is a similar C4, normally carrying break-bulk cargo on the North Atlantic run during the winter months. The WOLVERINE STIE experienced an average maximum peak-to-trough stress value in an interval of approximately 7400 psi at a sea state of - 10 while the BOSTON recorded an average maximum stress of slightly higher than

10,000 psi. From this figure it is apparent that the vertical bending stresses in the BOSTON are consistently and significantly higher than those experienced on the WOLVERINE STATE. All WOLVERINE STATE data used was appropriately corrected for plate unfairness and reflects the average value of combined port and star-board transducers. Reference ₃ elaborates on the development of this correction

factor. Table X provides the WOLVERINE STATE characteristics.

There is some noticeable scatter to parts of the data reflective of the various headings and speeds assumed by the vessels and somewhat by the uncertainty of attempting to establish exact Beaufort sea state by visual observations. In

general the average vertical bending stress on the BOSTON is about 66% higher than that on the WOLVERINE STATE. Approximately 16% of this can be attributed to the lower section modulus of the BOSTON (39,391 in2 ft) compared to the WOLVERINE STATE (45,631 in2 ft). Further examination into other possible causes for this discrepancy is continuing. Since the comparison is based on only 2 voyages for the BOSTON, it is anticipated that inclusion of data from the 1969-1970 season will provide a firmer basis for comment.

Figure 8 displays the horizontal longitudinal bending signal of channel 2 which is of considerably lower magnitude than the vertical component of channel 1. This difference in signal level clearly demonstrates, as predicted, that the verti-cal component is of significantly higher magnitude and of primary importance.

The torsional shear stress values presented in Figure 9 are quite low in magnitude, the maximum shear stress observed being approximately 1250 psi peak-to-trough. The location selected for these gages (discussed also in Ap-pendix A of reference1) at the neutral axis of the vessel resulted as a compro-mise of several differing opinions. Subsequent consideration among personnel at Teledyne and discussIons with Sea-Land technical personnel suggest that other loca-tions may provide slightly higher shear stress values, such as just below the box beam structure. Nevertheless, the present location does provide a reasonable measure of the severity of the torsional shear stress induced on the vessel, and

inasmuch as the magnitudes are very low, far from structural concern, there does not appear to be any immediate need to alter the instrumentation. As a comple-mentary approach to improve insight into the torsion behavior additional strain gages were installed on the transverse deck girder between hatches 5 and 6 on the starboard side. These strain gages will measure stresses induced by the double-S bending of the transverse member, thereby providing information on the severity

of the torsional distortion. These measurements will be made in the forthcoming voyages of the 1969-1970 winter season. The calibration test will also include distortional measurements of a hatch opening adjacent to the midship section.

The stress data from the four box beam gages was compared to the verti-cal longitudinal bending stress as a reference. The detailed location of these gages and the box beam plate thickness at these locations are indicated in Figure 5. Under ideal conditions of beam bending it is clear from the locations of Figure 5 that the upper three gages should show stress values very nearly equal to

those of the vertical bending deck gages which represent the maximum bending stress. The port side weld gage will exhibit stress values lower in proportion to its sinai-ler distance from the neutral axis.

r 10 H U) 8 Cl)

0

1=;:

0 S..S. BOSTON CORRECTED

S.S. WOLVERINE STATE DATA:

I F Note: 7 0

S.S. BOSTON SMLES

23 50 32 49

J

I

I.

1'. See Reference 4 F8igure

79

1

2

3

BEAUFORT SEA STATE

Fig. 22.

Vertical Longitudinal Bending

S.S. Wolverine State

North Atlantic Winter

S.S.

Boaton-VoyageS

#9 & #10

ii

4

S.S. WOLVERINE STATE SMLES

72 95. - 42 25 18 6 I I

I

4 5 6 7 8 9 10

F

0-14 12

28

Table X.

Characteristics Of The

S.S. Wolverine State

Original Name: MARINE RUNNER

Builder: Sun Shipbuilding and Drydock

Company.

Type: C4-S-B5 Machinery-Aft Dry

CargO Vessel = Official Number 248740 Length Overall. 520' 0" Length.BetweEn Perpendiculars: 496' - 0" Breadth, Molded: 71' - 6" Depth,, Molded: 54' - 0"

Depth, 'Molded

to Poop

Deëk .', 43' - 6"

Depth, Molded to.SecOnd.Deck .' 35' - 0"

Depth, Molded to Third Deck 26' 0"

Tonnage (U.S.) Gross: 10,747 ,

Net: 6,657

Load Drift, Molded (Design) ' 30' 0"

Load raft, Keel (Full Scantling) ' 32' - 97/8"

'

Light Ship Drafts 3' -7" .Fwd.

- ..- . ' - 19' - 9-1/2" aft .

'11' - 8-1/4" mean

Dead Weight (at 32' - 9-7/8") ,. . 1.5,348L.T.

Light Ship Weight 6,746 L.T.

Center of Gravity: . ' ' 30.4 ft. àbovE keel

24.2 ft. aft o midships. B.'P.

Block COefficient: ' 0.654 (30' Molded Design Draft)

Prismatic Coeficient:

Wátep1ane Coefficient:

Midship. Section Modulus:

Machiflery:

Steam Turbine with Double Reduction Gear

Normal Maximt

H.P. Turbine, Design R.P.M. 5,358

L.P. Turbine, Design R.P.M. 4,422

Propeller1 Design R.P.M. 85 88

Propeller, Normal Design R.P.M. 80

Shaft Horsepower, H.P. Turbine 4,500

Shaft Horsepower, L.P. Turbine 4,500

Shaft Horsepower, Total 9,000 9900

First Reduction Gear, H.P. Turbine

9O96

First Reduction Gear, L.P. Turbine 7.508

-Second Reduction Gear 6,930

It should be höted that eaëh of these. stress gages is monitOéd as a single active arm bridge. (See Figure 3D.) Consequently, longitudinal stresses induced by all stress modes are algebraically present in each gage in contrast

tot-he four-active arm bridges which can be and are so arranged to cancel stresses induced by stress modes other than that desired. Each single element gage

there-f ore provides the total longitudinal stress level present- at each loóation.

The data from each gage was examined on an instantaneous basis against bo'th the vertical and horizontal bending stresses to determine the contribution

of each to the total stress in the single element. Generally, there is very lit-tle stress contribution from horizontal bending, but on occasion values as high as 15 per cent of the vertical stress were observed. The percentages shown in Figure 5 represent the amount. of vertical bending stress at the location,relative to the deck location taken as 100 per cent. On thebasis of pure bending, it would be anticipated that the two gages SBBG and SSPG would show the same percentage values since the vertical positions are Identical. The inside gage SBBG exiTibits

about a 13 per cent drop in bending stress as compared to the 6 'per cent for SSPG which is moderately higher than that to be expected for the 7-inch shorter

dis-tánce from the neutral axis. This data indicates that some lag is present in the'.structural participation of the inside portion of the box beam; however, the magnitudes are not of major proportions. Inasmuch as the data acquired on these gages is time shared, and hence fewer data points are obtained, the accuracy of the valueswill be significantly improved with the added data of the forthôoming winter season.

0.664, (30' Molded Design Draft)

0.628 (18" Typical Present Operation)

0.752 (30' {oled Design Draft)

0,685 (18' Typical Present Operation)

45,631 in2 ft. (to top of Upper Deck

EZ

_{I 0} 8

OH

.6 1.4 1.2 10 30

Total stress values of these transducers, which includes horizontal and vertical bending plus stress induced by other modes, did not exceed 115 per cent of the vertical bending stress on any of the four gages. The major increment

to the total stress over and above the vertical bending stéss is attributed to the horizontal bending stress indicating that very little st-ress is contributed by all other modes.

4.3 AccelEration Data

Figures 10 through 15 display the six acceleration signals i.e., three vertical and three horizontal. _{The bow vertical signal of Figure 14 is the most}

significant. A comparison of the average value of this signal for voyages 9 and 10 of the S. S. BOSTON with the average value from 14 round trip voyages of the

S. S. WOLVERINE STATE is provided in Figure 23. A very close agreement was achieved as anticipated sincE such response is primarily a function of hull form which is not altered in the conversion of the vessel and hence remains similar to the S. S. WOLVERINE STATE.

The levels of acceleration sensed on the other five channels were sig-. nificantly below that of Figure 14 as theory predicts and thus are of secondary

interest. X S.S. BOSTON -

Q

S.S. WOLVERINE STATE

_A7

.4 x-..--..-x

Fig, 23. Wave-Induced Bow Vertical Acceleration

S.S. Boston

\byages #9 & #10

S.S.

Wolverine 1tatel4

Roundtripbyages

1 2 3 5 6 9 10

4.4 Ship's Motion Data

Figures 16 and 17 (pitch and roll) describe the attitude of the vessel

in the various sea conditions-. Close observation of this information displays quite clearly the unique mode of- operation peculiar to container vessels. In

order to prevent- possible damage to on-deck containers, the ship's master is in-clined to avoid head seas and reduce the pitch at the cost of increasing the roll. Naturally, a trade of f is made between ship's speed and the macimum pitch and

roll permitted. The tendency is to be in a roll mode even during light seas verified by our operating personnel during the- past season. In addition to

con-tributing to the discomfort factor, this phenomenon-limits the extent of data analysis which may be accomplished while at sea.

-It can be observed from Figure 16 that pitch is predominantly under 6 degrees double amplitude or only 3 degrees on the average from the horizontal. This low degree of pitch certainly would keep the amount of water taken over the bow- to a minimum and prevent damage to the on-deck container. -

-The roll information of Figure 17 displays a much greater angle. Even at sea states of 3 and 4, rolls of 10 degrees or more to the- vertical are quite common. The pitch and roll signals when correlated with the log book data, provide the in-house personnel with a good picture of what took place on the vessel on a Winter's

crossing. - - -

-4.5 Supplementary St-rain Gage Data

No. plots of the supplementary data were - provided for the past season since these devices were installed primarily to validate the accuracy of the stress gage transducers insuring against the influence of local effects. The two units, one port and the other starboard, were recorded on alternate days. A

comparison of the data channel showed a consistency of data between the two units. A periodic conversion of the stress data was made and compared to the vertical

stress data with good results. A typical comparison gave a reading of 9090 ps-i on channel 1, a value of 9,000 psi on chaonel 4A (SUDG) and a supplementary gage value of 9,240 psi.

The 1969-1970 season will find each interval of supplementary strain gage data accomplished by a calibration signal which should allow for a much

bet-ter presentation of the available data. It is still planned

to

record these de-vices on, alternate days on the same channel.

4.6 Wave Buoy Data

Wave buoy data for two out of the three launches was reduced, on the Teledyne Materials Research Power Spectral Density Program to provide the out-puts shown on Figures 18-20. In. addition, a computer analysis of channel 1

verti-cal longitudinal bending stress was performed on data taken during the wave buoy recordfng period. An RMS value, as well as the maximum peak-to-trough signal for each interval, is obtained from this computation. Spectral data should be con-sidered conditional until final analyses are completed.

The analysis of the first un-it, buoy 49004 generated a standard dévià-tion of the displacement signal of 7.83 ft. RMS. Arbitrarily calling a "signi-ficant" wave height four times the RMS, one finds the significant wave height would be about 30 feet. _{A comparison of log book data for this period of time} in-dicated an average wave height of 20 feet and an average swell height of 25 feet. These visualobservations were difficult to interpret, but the wave buoy results seem to be of the same order of magnitude. _{The computer printout generated an RMS}

32

stress value ranging from about 3000 psi to 5000 psi for these intervals with a maximum peak-to-trough value of 11000 psi.

The Second launch of buoy 49001 provided an RNS displacement of 2.813 ft. Four times this amount gives a corresponding significant sea of 11 25 feet Log book data listed an average wave height 'of 5-feet with a5 to 6 foot swell running. The range of RHSvertical stress was from,2600 psi to 4600 psi with a-maximum

peak-to-trough value of 10,000 psi; -

-A comparison of -sea:states of the two launches (the first at 8-9 and the second at 5-6) appeared consistent with the -values obtained;, certainly, they

shift in the proper direction.

-5.0 CONCLUSIONS

On the basis o two voyages during the 1968-1969 season the data indicate that the longitudinal bending 'stresses are significantly higher for the converted structure of the S.. S. BOSTON as compared to a similar. class C-4 before conversion,

e.g., S. S. WOLVERINE STATE'. The level of the stress values is nevertheless' not of sufficient magnitude to be of structural- cOncern for the sea states

en-countered.- - -

-Although the shear stress transducers may not be located a the precise region of maximum torsional shear, it is appa±ent that values two to three times those observed, which is considered quite unlikely, would not be of structural

con-cern. Therefore, if one considers the very low values, little- advantage would be gained by the addition of more totsional shear t-ransducers at other locations.' Tor-sional distortions are, however,--of importance, and additional instrumentation has been introduced into the program to obtain torsional deformation data during both

the calibration test and seaway voyages. - -

-Stress intensification data obtained on the BOSTON box beam indicates some lag in' participation of the inside portion of the box beam; -however, additional

dat-a is required before definitive values can be obtaIned. - -

-A recently completed static test on the BOSTON (see subsequent report) in-dicated good agreement between asured torsion a±td bending stress changes and those calculated from the app-lied twist and bending moments. The data re-ported herein can therefore be ireated with some confidence.

REFERENCES

Fain, R. A. Cragin, 3. Q., Schofield,, B.. H. "Deigri and Installa-tion of Ship Response InstrumentaInstalla-tion System Aboard the Container Vessel S.S. BOSTON." Ship St'tuètuIè Committee Report SSC-211, 1970.

Wheaton, J. W. "Wave Height Measurement Test." Teledyne Materials Research Technical Report No. E-1184, 25 Augut 1969.

Fritch, D. J., Bai1e, Wheaton, J.W. "Reult From Full-Scale Measurements of Midship Bending Stresses 'on TwO Dry-Cargo Ships

--Report No. 2. Ship Str!.lcture Committee Report ssÔ-181, March 1967

Bailey, F. C., Walters, I. J., "Results Ftom Full-Scale Measurements

of Midship Bending Stresses on Three Dry Cargo ShIpst' - Ship Structure

34

APPENDIX A

TRANSDUCER SPECIFICATIONS

Stress Gages

BLH Electronics, Inc., Type FAB-28-S6

Longitudinal Gage Resistance: 350.0 + 2.5 Ohms Gage Factor: 2.06 ± 1% Lateral Gage Resistance: 98.0 ± 1.0 Ohms Gage.actor: 2.05 ± 1% Poisson Ratio: .28 ± 1%

Stress Gage Factor: 1.48 ± 1%

Torsion Gages

BLH Electronics, Inc., FABD-25-12S6

Gage Factor: 2.02± 1%

Resistance: 120.0 ± .2 Ohms

Bow and Stern Accelerometers

Setra Inc., Model 100

Range: ± 5g

Maximum Static Acceleration: ± lOOg Approximate Natural Frequency: 490 Hz Transverse Acceleration Response: <0.Olg/g

Excitation: 6 VDC at 20 ma Full Range Output: ± 1.5 VDC Output Impedance: 400 Ohms

MidshIps Accelerometers

Statham Instruments, Inc., Model A3-2.5 - 350

Range: ± 2.5g

Nominal Bridge Resistance: 350 Ohms Approximate Natural Frequency: 55 Hz

Transverse Acceleration Response 0.02g/g

Excitation:. Ii Volts DC or AC (RMS) Full-Scale Output: ±. 20 my

Used with Statham Instruments

Model CA9-56 Strain Gage Signal Amplifier with an output of ± 2.5 VDC

'5. Midships Pitch-and-Roll Signals

Humphrey Inc., Pendulum Transducers, Model CP17-0601-1

Range: ± 45° ± 0.5°

Resistance: 2000 Ohms + 5%

-

0

Power Dissipation: 0.5 watt at 130 F

Accuracy ± 17 with straight line approximation Natural Frequency: 2 Hz

Displacement. Transducers

Hewlett Packard, Model 7DCDT-050

Full-Scale Output: 1,5 VDC Range: ± 0.050 inches. Sdale Facto±:

30 Win

Maximum Nonlinearity: ±.05% FS Excitation Voltage: 6 VDC Nominal Output Impedance: 2.2 K Ohms

Frequency Response:

34b do

at 350 Hz

Wave Data Acquisition System

Eãstéch Limited,Windsor, NovaScotia, Model 440

Used with Model 266 Wave Buoys.

Data recorded as positive pulses approximately 3 milliseconds in duration, approximately 1.5 volts peak at 30 pulses per second at zero acceleration

36

APPENDIX B

-CALIBRATION MODE CALCULA:rIONS

The four stress/strain gage bridge circuits which pràvidè the

data for channels 1-4, shown on Figures 3A to 3D, are placed ma

calibration mode by paralleling a known fixed precision resistance

across one arm of thebridge. This action creates an output signal

equivalent to a precalculated output The following discussion

develops the procedure used to establish t1ie value of c71ibràto

resistor and stress level achieved

For stress gages the following equation wasderived based on a

4-arm bridge circuit made up o gage elements anda. fixed resistor

(R) used to provide shunt calibrtipi

ERM

R

-

(GF) TN

cc

where R is the value of the calibration resistor in ohms

C

E Modulus of elasticity taken to be 30 x lo6 psi for steel

= Combined gage resistance i.e., longitudinal plus lateral components; 448 ohms for the gages used in this system

= Number of, stress gages per arm

(GF) = The combined gage factor; 1.48 for the stress c

gages used

Tc = The calibration stress in psi

For thannels 1 and 2 (Figures 3A and 3B) a 445 -k-ilóI ca1ibration re-sistor was ued. This ä1ue produces a calibration stress equivalent to:

C

ER M

(GF )R N

cc

20,400 psi

The other channel using stress gages is channel 4 (Fig 3D) In this

arrangement M and N = 1. R was selected as 889 kilohms, thus:

10,200 psi

Channel 3 signal is provided by a strain gage bridge rather than a

stress gage circuit The equation is modified slightly to include the

effects of (.i) Poisson's ratio. For a bridge circuit made up of 4

active strain gage elements: of 120 ohms each, a gage factor of 2,

= 0.28 anda calibration resistor of 183 kilohs. The resulting

equation becomes:

ER

with M and N

= 1921 psi

The transducers for channels 5-12 are devices which provide a f-ied

gradient of output ie., ± 0.3v/g or 0.lv/degree. To provide a

cali-bration signal, a precision voltage source is established at the

trans-ducer to generate a specified voltage whn the system is in a calibration mode.

38

These calibration signals are as follows:

Channel 13 information is developed from displacement gages. No

calibration mode signals are generated for this signal. A physical

calibration of these units was performed at the time of installation

and will be repeated during the upcoming calibration tests. Channel 14

is the compensation channel, and again no calibration signal is

gener-ated or required. A short across the input provides for a 0 volt input

i.e., the center frequency of the oscillator is not changed. Any change

of the frequency and subsequent output signal would be the result of the

recorder itself causing a shift of frequency due to its environment.

This signal is used to control the recorder in the play-back mode, and

the data is thus corrected for any deviation.

Channel Function.

Calibration voltage-unit

5 Stern Verical Acceleration 0.3v lg

6 Stern Horizontal Acceleration 0.3v .= ig

7 Midships Vertical Acceleration lv = 2g

8 Midships Horizontal Acceleration lv 20°

9 Pitch lv = 20°

10 Roll lv = 20°

11 Bow Vertical Acceleration 0. 3v Ig

Security

Classification

D D

1JAN64FORM UNCLASSIFIED

Security Classification

DOCUMENT CONTROL DATA- R&D

(Security claeaification of title body of abstract and indesfog annotation must be entered when the overall report a classified)

1. ORIGINATING ACTIVI'Y (Ce.porate athor

-TELEDYNE MATERIALS RESEARCH 303 Bear Hill Road

Waltham, MA 02154

2e. REPORT SECURITY C LASSIFICATION Unclassified

2b. GROUP

-3. REPORT TITLE

Results from the First Operational Season of Container Vessel S S Boston in North Atlantic.

4. DESCRIPTIVE NOTES (Type of ieport and inclusive dates)

-Technical Report- July 1968 - 1 October 1969 5. AUTHOR(S) (Last name, first neme initial)

Richard A. Fain, Bradford H. Schofield, and John Q. Cragin

6. REPORT DATE

July-1970 .

7a. TOTAL NO. OF PAGES -

-. 38 7b. NO. OF REFS 6 Be CONTRACT OR GRANT NO N00024-68-c-5486 . . b. PROJECT NO. . F-35422306 . Task 2022 SR 182 . : .

9a ORIGINATOR S REPORT NUMBER(S) .

E-1123-4

pOINo(S (Aàyóthernumbers that may be aesiied

this report

. SSC

10. AVAILABILITY/LIMIT.TION NOTICES -

-Distribution of this document,SSC-212 is unlimited.

II. SUPPLEMENTARY NOTES - 12. SPONSORING MILITARY ACTIVITY

-Naval Ship Systems Command

13. ABSTRACT .

:

. .

-This report contains data, with associated discussions, collected from the Sea-Land Vessel S S BOSTON, during the operating season, November 1968 to

UNCLAscirirn

Securitylâitfation

Container Vessel Instrumentation

Shipboard Instrumentation System

North Atlantic Crossings

Bending Stresses

Accelerations

Torsional Stress

Power Spectral Density Analysis

LINK A ROLE WT LINK B ROLE WT LINK C ROLE WT

i,

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14.